The instant invention relates to an improved aerosol dispenser assembly that dispenses a liquid product as a fine spray having a reduced particle size, while reducing the amount of propellant required to dispense the liquid product from the container.
Aerosol dispensers have been commonly used to dispense personal, household, industrial, and medical products, and to provide a low cost, easy to use method of dispensing a liquid product. Typically, aerosol dispensers include a container, which contains a liquid product to be dispensed, such as soap, insecticide, deodorant, disinfectant, or the like. A propellant is used to discharge the liquid product from the container. The propellant is under pressure and provides a force to expel the liquid product from the container when a user actuates the aerosol dispenser by, for example, pressing an actuator button.
The two main types of propellants used in aerosol dispensers today are liquefied gas propellants, such as hydrocarbon and hydrofluorocarbon (HFC) propellants, and compressed gas propellants, such as compressed carbon dioxide or nitrogen gas. To a lesser extent, chlorofluorocarbon propellants (CFCs) are also used. The use of CFCs is, however, being phased out due to the harmful effects of CFCs on the environment.
In an aerosol dispenser using the liquefied gas-type propellant (also known as a double phase propellant), the container is loaded with the liquid product and propellant, and pressurized to a pressure approximately equal to, or slightly greater than, the vapor pressure of the propellant. Since the container is pressurized to the vapor pressure of the propellant, a majority of the propellant is liquefied. However, a small portion of the propellant will remain in gaseous form. As the product is dispensed, the pressure within the container will decrease and more of the propellant will enter the gas phase. In a compressed gas aerosol dispenser, the propellant remains in gaseous form when the container is pressurized for use.
A conventional aerosol dispenser generally comprises a container (not shown) for holding a liquid product and a propellant, and a valve assembly for selectively dispensing a liquid product from the container. As illustrated in FIG. 3, the valve assembly 104 comprises a mounting cup 106, a mounting gasket 108, a valve body 10, a valve stem 112, a stem gasket 114, an actuator cap 116, and a return spring 118. The valve stem 112, stem gasket 114, and return spring 118 are disposed within the valve body 110 and are movable relative to the valve body 110 to selectively control dispensing of the liquid product. The valve body 110 is affixed to the underside of the mounting cup 106, such that the valve stem 112 extends through, and projects outwardly from, the mounting cup 106. The actuator cap 116 is fitted onto the outwardly projecting portion of the valve stem 112 and is provided with an actuator orifice 132. The actuator orifice 132 directs the spray of the liquid product into the desired spray pattern. A dip tube 120 is attached to the lower portion of the valve body 110 to supply the liquid product to the valve assembly 104 to be dispensed. As shown in FIG. 2, the whole valve assembly 104 is sealed to a container 102 by mounting gasket 108.
In operation, when the actuator cap 116 of the dispenser 101 is depressed, the propellant forces the liquid product up the dip tube 120 and into the valve body 110 via a body orifice 122. In the valve body 110, the liquid product is mixed with additional propellant supplied to the valve body 110 through a vapor tap 124. The vapor tap 124 helps to mix the liquid product and propellant in the valve body 110, to thereby break up the product into smaller particles suitable to be dispensed. From the valve body 110, the product is propelled through a stem orifice 126, out the valve stem 112, and through an actuator orifice 132 formed in the actuator cap 116.
S. C. Johnson and Son, Inc. (S. C. Johnson) employs an aerosol valve similar to that shown in FIG. 3 in connection with their line of Glade(copyright) aerosol air fresheners. The propellant used to propel the air freshener liquid product from the container is a B-Series propellant having a propellant pressure of 40 psig (B-40), at 70xc2x0 F. (2.722 atm at 294.261 K). xe2x80x9cPropellant pressurexe2x80x9d refers to the approximate vapor pressure of the propellant, as opposed to xe2x80x9ccan pressure,xe2x80x9d which refers to the initial gauge pressure contained within a full aerosol container. The B-40 propellant is a composition of propane, normal butane, and isobutane. By normal butane it is meant the composition denoted by the chemical formula C4H10, having a linear backbone of carbon. In order to effectively dispense this air freshener composition, the aerosol dispenser used by S. C. Johnson in connection with their line of Glade(copyright) aerosol air fresheners has a stem orifice diameter of 0.025xe2x80x3 (0.635 mm), a vapor tap diameter of 0.020xe2x80x3 (0.508 mm), a body orifice diameter of 0.062xe2x80x3 (1.575 mm), and a dip tube inner diameter of 0.060xe2x80x3 (1.524 mm). This current Glade(copyright) aerosol air freshener requires that the B-40 propellant be present in the amount of approximately 29.5% by weight of the contents of the dispenser assembly.
Hydrocarbon propellants contain Volatile Organic Compounds (VOCs). The content of VOCs in aerosol air fresheners is regulated by various federal and state regulatory agencies, such as the Environmental Protection Agency (EPA) and California Air Resource Board (CARB). S. C. Johnson continuously strives to provide environmentally friendly products and regularly produces products that exceed government regulatory standards. It is in this context that S. C. Johnson set out to reduce the content of VOCs in their line of Glade(copyright) aerosol air fresheners.
One way in which to reduce the VOC content in such aerosol air fresheners is to reduce the content of the hydrocarbon propellant used to dispense the liquid product. However, we have discovered that a reduction in the propellant content adversely affects the product performance. Specifically, reducing the propellant content in the aerosol air freshener resulted in excessive product remaining in the container at the end of the life of the dispenser assembly (product retention) and an increase in the size of particles of the dispensed product (increased particle size). It is desirable to minimize the particle size of a dispensed product in order to maximize the dispersion of the particles in the air and to prevent the particles from xe2x80x9crainingxe2x80x9d or xe2x80x9cfalling outxe2x80x9d of the air. Thus, we set out to develop an aerosol dispenser assembly that can satisfactorily dispense an aerosol product that contains, at most, 25% by weight, of a double phase hydrocarbon propellant, while actually improving product performance throughout the life of the dispenser assembly.
The xe2x80x9clife of the dispenser assemblyxe2x80x9d is defined in terms of the pressure within the container (i.e., the can pressure), such that the life of the dispenser assembly is the period between when the pressure in the container is at its maximum and when the pressure within the container is substantially depleted, i.e., equal to atmospheric pressure.
One known method of reducing the particle size of a dispensed liquid product is disclosed in U.S. Pat. No. 3,583,642 to Crowell et al. (the ""642 patent), which is incorporated herein by reference. The ""642 patent discloses a spray head that incorporates a xe2x80x9cbreakup barxe2x80x9d for inducing turbulence in a product/propellant mixture prior to the mixture being discharged from the spray head. Such turbulence contributes to reducing the size of the mixture particles discharged from the spray head.
Our invention provides an improved aerosol dispenser assembly that dispenses substantially all of a liquid product (i.e., reduces product retention) as a fine spray having reduced particle size, while at the same time reducing the amount of propellant required to dispense the liquid product from the container.
In one aspect, an aerosol dispenser assembly according to our invention comprises a container that contains a liquid product and a propellant for propelling the liquid product from the container. The propellant is a dual phase hydrocarbon propellant, is free of normal butane, and constitutes at most 25% by weight of the contents of the container. The contents of the container are pressurized to between about 55 psig (3.743 atm) and about 120 psig (8.166 atm). In particular, the contents of the container are pressurized to between about 55 psig (3.743 atm) and about 80 psig (5.444 atm).
A valve is attached to the container for selectively dispensing the liquid product from the container as a mist, the mist having an average particle size of less than 35 xcexcm (0.0014xe2x80x3), over at least 75% of the life of the dispenser assembly. Average particle size, as used herein, means average mean particle size D(V,0.5) of the dispensed product, as measured by a Malvern(copyright) Mastersizer 2600 Particle Size Analyzer. In addition, the dispenser assembly is capable of dispensing over 98% by weight of the liquid product from the container.
A vapor tap is formed in the valve to facilitate thorough mixing of the propellant and the liquid product prior to dispensing, and a valve stem is disposed in the valve. The valve stem defines at least one stem orifice for flow of the product during dispensing. The vapor tap has a diameter of about 0.013xe2x80x3 (0.330 mm) to about 0.019xe2x80x3 (0.483 mm).
A dispenser cap is mounted on the valve stem for actuating the valve to dispense the liquid product. The dispenser cap defines an exit path, through which the liquid product can be dispensed. A breakup bar is positioned in the exit path of the dispenser cap to break up the liquid product in order to reduce the size of the particles before the liquid product is dispensed.
A better understanding of these and other aspects, features, and advantages of the invention may be had by reference to the drawings and to the accompanying description, in which preferred embodiments of the invention are illustrated and described.